The present invention is directed to aircraft docking systems and more particularly to safety enhancements for aircraft docking systems for automatic checking of the apron for obstacles before and during docking and for detection of fog and snowfall in front of the docking system. The present invention is further directed to methods implemented on such systems.
In recent years, there has been a significantly increased number of passenger, cargo and other aircraft traffic, including takeoffs, landings and other aircraft ground traffic. Also, there has been a marked increase in the number of ground support vehicles which are required to offload cargo and to provide catering services and ongoing maintenance and support of all aircraft. With that substantial increase in ground traffic has come a need for greater control and safety in the docking and identification of aircraft on an airfield.
To that end, U.S. Pat. No. 6,023,665, issued Feb. 8, 2000, to the same inventor named in the present application and hereby incorporated by reference into the present disclosure, teaches a system for detecting, identifying and docking aircraft using laser pulses to obtain a profile of an object in the distance. The system initially scans the area in front of the gate until it locates and identifies an object. Once the object is identified as an airplane, the system tracks the airplane. By using the information from the profile, the system can in real time display the type of airplane, the distance from the stopping point and the lateral position of the airplane. The modes of operation of the system include a capture mode, in which an object is detected and determined to be an aircraft, and a tracking mode, in which the type of aircraft is verified and the motion of the aircraft toward the gate is monitored.
Referring to FIG. 1A, the docking guidance system of the above-referenced patent, generally designated 10, provides for the computerized location of an object, verification of the identity of the object and tracking of the object, the object preferably being an aircraft. In operation, once the control tower 14 lands an aircraft 12, it informs the system that the aircraft is approaching a gate 16 and the type of aircraft (i.e., 747, L-1011, etc.) expected. The system 10 then scans the area 19 in front of the gate 16 until it locates an object that it identifies as an airplane 12. The system 10 then compares the measured profile of the aircraft 12 with a reference profile for the expected type of aircraft and evaluates other geometric criteria characteristic of the expected aircraft type. If the located aircraft, at a minimum specified distance (e.g., 12 m) before the stop position, does not match the expected profile and the other criteria, the system informs or signals the tower 14, displays a stop sign and shuts down.
If the object is the expected aircraft 12, the system 10 tracks it into the gate 16 by displaying in real time to the pilot the distance remaining to the proper stopping point and the lateral position of the plane 12. The lateral position of the plane 12 is provided on a display 18 allowing the pilot to correct the position of the plane to approach the gate 16 from the correct angle. Once the airplane 12 is at its stopping point, that fact is shown on the display 18 and the pilot stops the plane.
Referring to FIG. 1B, the system 10 includes a Laser Range Finder (LRF) 20, two mirrors 21, 22, a display unit 18, two step motors 24, 25, and a microprocessor 26. Suitable LRF products are sold by Laser Atlanta Corporation and are capable of emitting laser pulses, receiving the reflections of those pulses reflected off of distant objects and computing the distance to those objects.
The system 10 is arranged such that there is a connection 28 between the serial port of the LRF 20 and the microprocessor 26. Through that connection, the LRF 20 sends measurement data approximately every {fraction (1/400)}th of a second to the microprocessor 26. The hardware components generally designated 23 of the system 20 are controlled by the programmed microprocessor 26. In addition, the microprocessor 26 feeds data to the display 18. As the interface to the pilot, the display unit 18 is placed above the gate 16 to show the pilot how far the plane is from its stopping point 29, the type of aircraft 30 the system believes is approaching and the lateral location of the plane. Using that display, the pilot can adjust the approach of the plane 12 to the gate 16 to ensure the plane is on the correct angle to reach the gate. If the display 18 shows the wrong aircraft type 30, the pilot can abort the approach before any damage is done. That double check ensures the safety of the passengers, plane and airport facilities because if the system tries to dock a larger 747 at a gate where a 737 is expected, it likely will cause extensive damage.
In addition to the display 18, the microprocessor 26 processes the data from the LRF 20 and controls the direction of the laser 20 through its connection 32 to the step motors 24, 25. The step motors 24, 25 are connected to the mirrors 21, 22 and move them in response to instructions from the microprocessor 26. Thus, by controlling the step motors 24, 25, the microprocessor 26 can change the angle of the mirrors 21, 22 and aim the laser pulses from the LRF 20.
The mirrors 21, 22 aim the laser by reflecting the laser pulses outward over the tarmac of the airport. In the preferred embodiment, the LRF 20 does not move. The scanning by the laser is done with mirrors. One mirror 22 controls the horizontal angle of the laser, while the other mirror 21 controls the vertical angle. By activating the step motors 24, 25, the microprocessor 26 controls the angle of the mirrors and thus the direction of the laser pulse.
The system 10 controls the horizontal mirror 22 to achieve a continuous horizontal scanning within a xc2x110 degree angle in approximately 0.1 degree angular steps which are equivalent to 16 microsteps per step with the Escap EDM-453 step motor. One angular step is taken for each reply from the reading unit, i.e., approximately every 2.5 ms. The vertical mirror 21 can be controlled to achieve a vertical scan between +20 and xe2x88x9230 degrees in approximately 0.1 degree angular steps with one step every 2.5 ms. The vertical mirror is used to scan vertically when the nose height is being determined and when the aircraft 12 is being identified. During the tracking mode, the vertical mirror 21 is continuously adjusted to keep the horizontal scan tracking the nose tip of the aircraft.
While the system disclosed in the above-cited patent detects the airplane, that system does not detect ground support vehicles or other objects in the apron of the docking area. Because of the pilot""s limited field of view, the aircraft may collide with such ground support vehicles or other objects. Also, the system may give erroneous warnings in fog or snow, particularly the former.
Fog is most often seen between 10-25 m by the system. As that distance is closer, or in the area of, the stop position, the system will generate a gate blocked or ID-fail condition if the capture procedure triggers on the fog. The capture procedure needs a method to recognize that the object captured is most likely fog and is no obstruction to the docking procedure once the aircraft appears.
Log files taken during foggy conditions show that fog is reported like a solid object in front of the system. A sweep into fog often reports close to 100% echoes, and the echoes vary in distance only with a few decimeters of each other. Snowfall is most often more spread out, giving 60-80% echoes with a spread of 5-10 m. Thus, snow is generally easier to detect, i.e., discriminate from a solid object, than fog is. FIGS. 2A and 2B show sample images of fog, while FIGS. 2C and 2D show sample images of snow.
It will be apparent from the above that a need exists in the art for an aircraft detection system which overcomes the above-noted problems of the prior art. It is therefore an object of the present invention to permit detection of objects in the apron.
It is another object to support the pilot""s judgment as to whether it is safe to proceed to the gate or there is a risk of collision.
It is another object of the present invention to permit accurate detection of fog and snow.
To achieve the above and other objects, the present invention is directed to a system and method for aircraft detection in which the apron is automatically checked for obstacles before and during docking. As the aircraft may be approaching the gate at a high speed, it is essential that checking for obstacles occupy the system for the minimum amount of time so that the influence on the docking function is minimized. It is assumed to be particularly important that the area is checked which is swept by the wings of a narrow-body aircraft or swept by the engines of a wide-body aircraft. It is also assumed that it is not so important to check the apron at the bridge side of the center line as it is to check the opposed side, as most movements of service vehicles take place on the opposed side. Therefore, it is assumed that the scanner unit can be mounted such that the optical axis points to the left of the center line, e.g., 5xc2x0, thus taking maximum advantage of the horizontal scanning range of the system.
The present invention is further directed to a system and method for aircraft detection in which fog and snowfall are detected by analyzing the laser sweep triggering the capture condition. If the measured distance to the caught object is found to vary randomly (in a non-deterministic way) across the width of the object, the object is considered to be a possible fog/snow condition. A possible fog condition is not considered by the system as a valid target for the tracking phase, so that the system remains in capture mode. If the fog condition prevails, the system informs the pilot/stand operator by displaying a warning message. Under those conditions, it is intended that the pilot shall continue, with caution, to approach the stand area, as the system will be able to pick up the aircraft as soon as it is seen through the fog.
When a fog condition has been detected, the display switches from the standard capture display to a display showing the aircraft type alternating with a message such as xe2x80x9cDOWNGRADEDxe2x80x9d or xe2x80x9cLOW VISBxe2x80x9d to indicate that the system has downgraded performance due to reduced visibility. A corresponding message is displayed in the operator panel.
Any embodiment, or combination of embodiments, of the present invention can be implemented in the system of the above-referenced patent by appropriate modification.